Zophar repeats the same idea for emphasis. Zophar is saying that these are things that Job would do if he had done what Zopahr spoke of in verses 13 and 14. (See: [[rc://en/ta/man/translate/figs-parallelism]] and [[rc://en/ta/man/translate/figs-hypo)
"Take your rest" here is an idiom for "rest." The phrase "in safety" can be expressed with the word "safely." Alternate translation: "would rest safely" (See: [[rc://en/ta/man/translate/figs-idiom]] and [[rc://en/ta/man/translate/figs-abstractnouns]])